Many processes involve the sampling of bulk variable feedstocks, and this has especial importance where the feedstock contains one or more high value components. For example, in the recycle and refining of waste catalysts, or other wastes containing materials such as the platinum group metals, silver and gold, the refining organisation needs to determine levels of such metals in the bulk material to assess the value of metals to be credited to the owner of the bulk material. There is a need for improved sampling methods and, accordingly, for improved metal assays.